Cursor position, selection highlights and mouse clicks are now all

transformed back and forth according to the character position
permutation output from the bidi algorithm. I was expecting that to
be a lot harder.

[originally from svn r4915]

terminal.c

@@ -4317,8 +4317,11 @@ static int term_bidi_cache_hit(Terminal *term, int line,
 }
 
 static void term_bidi_cache_store(Terminal *term, int line, termchar *lbefore,
-				  termchar *lafter, int width)
+				  termchar *lafter, bidi_char *wcTo,
+				  int width)
 {
+    int i;
+
     if (!term->pre_bidi_cache || term->bidi_cache_size <= line) {
 	int j = term->bidi_cache_size;
 	term->bidi_cache_size = line+1;
@@ -4344,127 +4347,42 @@ static void term_bidi_cache_store(Terminal *term, int line, termchar *lbefore,
     term->pre_bidi_cache[line].chars = snewn(width, termchar);
     term->post_bidi_cache[line].width = width;
     term->post_bidi_cache[line].chars = snewn(width, termchar);
+    term->post_bidi_cache[line].forward = snewn(width, int);
+    term->post_bidi_cache[line].backward = snewn(width, int);
 
     memcpy(term->pre_bidi_cache[line].chars, lbefore, width * TSIZE);
     memcpy(term->post_bidi_cache[line].chars, lafter, width * TSIZE);
+    memset(term->post_bidi_cache[line].forward, 0, width * sizeof(int));
+    memset(term->post_bidi_cache[line].backward, 0, width * sizeof(int));
+
+    for (i = 0; i < width; i++) {
+	int p = wcTo[i].index;
+
+	assert(0 <= p && p < width);
+
+	term->post_bidi_cache[line].backward[i] = p;
+	term->post_bidi_cache[line].forward[p] = i;
+    }
 }
 
 /*
- * Given a context, update the window. Out of paranoia, we don't
+ * Prepare the bidi information for a screen line. Returns the
- * allow WM_PAINT responses to do scrolling optimisations.
+ * transformed list of termchars, or NULL if no transformation at
+ * all took place (because bidi is disabled). If return was
+ * non-NULL, auxiliary information such as the forward and reverse
+ * mappings of permutation position are available in
+ * term->post_bidi_cache[scr_y].*.
  */
-static void do_paint(Terminal *term, Context ctx, int may_optimise)
+static termchar *term_bidi_line(Terminal *term, struct termline *ldata,
+				int scr_y)
 {
-    int i, it, j, our_curs_y, our_curs_x;
-    int rv, cursor;
-    pos scrpos;
-    wchar_t *ch;
-    int chlen;
-    termchar cursor_background;
-#ifdef OPTIMISE_SCROLL
-    struct scrollregion *sr;
-#endif /* OPTIMISE_SCROLL */
-
-    cursor_background = term->basic_erase_char;
-
-    chlen = 1024;
-    ch = snewn(chlen, wchar_t);
-
-    rv = (!term->rvideo ^ !term->in_vbell ? ATTR_REVERSE : 0);
-
-    /* Depends on:
-     * screen array, disptop, scrtop,
-     * selection, rv, 
-     * cfg.blinkpc, blink_is_real, tblinker, 
-     * curs.y, curs.x, cblinker, cfg.blink_cur, cursor_on, has_focus, wrapnext
-     */
-
-    /* Has the cursor position or type changed ? */
-    if (term->cursor_on) {
-	if (term->has_focus) {
-	    if (term->cblinker || !term->cfg.blink_cur)
-		cursor = TATTR_ACTCURS;
-	    else
-		cursor = 0;
-	} else
-	    cursor = TATTR_PASCURS;
-	if (term->wrapnext)
-	    cursor |= TATTR_RIGHTCURS;
-    } else
-	cursor = 0;
-    our_curs_y = term->curs.y - term->disptop;
-    {
-	/*
-	 * Adjust the cursor position in the case where it's
-	 * resting on the right-hand half of a CJK wide character.
-	 * xterm's behaviour here, which seems adequate to me, is
-	 * to display the cursor covering the _whole_ character,
-	 * exactly as if it were one space to the left.
-	 */
-	termline *ldata = lineptr(term->curs.y);
-	our_curs_x = term->curs.x;
-	if (our_curs_x > 0 &&
-	    ldata->chars[our_curs_x].chr == UCSWIDE)
-	    our_curs_x--;
-	unlineptr(ldata);
-    }
-
-    /*
-     * If the cursor is not where it was last time we painted, and
-     * its previous position is visible on screen, invalidate its
-     * previous position.
-     */
-    if (term->dispcursy >= 0 &&
-	(term->curstype != cursor ||
-	 term->dispcursy != our_curs_y ||
-	 term->dispcursx != our_curs_x)) {
-	termchar *dispcurs = term->disptext[term->dispcursy]->chars +
-	    term->dispcursx;
-
-	if (term->dispcursx > 0 && dispcurs->chr == UCSWIDE)
-	    dispcurs[-1].attr |= ATTR_INVALID;
-	if (term->dispcursx < term->cols-1 && dispcurs[1].chr == UCSWIDE)
-	    dispcurs[1].attr |= ATTR_INVALID;
-	dispcurs->attr |= ATTR_INVALID;
-
-	term->curstype = 0;
-    }
-    term->dispcursx = term->dispcursy = -1;
-
-#ifdef OPTIMISE_SCROLL
-    /* Do scrolls */
-    sr = term->scrollhead;
-    while (sr) {
-	struct scrollregion *next = sr->next;
-	do_scroll(ctx, sr->topline, sr->botline, sr->lines);
-	sfree(sr);
-	sr = next;
-    }
-    term->scrollhead = term->scrolltail = NULL;
-#endif /* OPTIMISE_SCROLL */
-
-    /* The normal screen data */
-    for (i = 0; i < term->rows; i++) {
-	termline *ldata;
     termchar *lchars;
-	int dirty_line, dirty_run, selected;
+    int it;
-	unsigned long attr = 0, cset = 0;
-	int updated_line = 0;
-	int start = 0;
-	int ccount = 0;
-	int last_run_dirty = 0;
-
-	scrpos.y = i + term->disptop;
-	ldata = lineptr(scrpos.y);
-
-	dirty_run = dirty_line = (ldata->lattr !=
-				  term->disptext[i]->lattr);
-	term->disptext[i]->lattr = ldata->lattr;
 
     /* Do Arabic shaping and bidi. */
     if(!term->cfg.bidi || !term->cfg.arabicshaping) {
 
-	    if (!term_bidi_cache_hit(term, i, ldata->chars, term->cols)) {
+	if (!term_bidi_cache_hit(term, scr_y, ldata->chars, term->cols)) {
 
 	    if (term->wcFromTo_size < term->cols) {
 		term->wcFromTo_size = term->cols;
@@ -4534,21 +4452,158 @@ static void do_paint(Terminal *term, Context ctx, int may_optimise)
 		if (term->wcTo[it].origwc != term->wcTo[it].wc)
 		    term->ltemp[it].chr = term->wcTo[it].wc;
 	    }
-		term_bidi_cache_store(term, i, ldata->chars,
+	    term_bidi_cache_store(term, scr_y, ldata->chars,
-				      term->ltemp, ldata->size);
+				  term->ltemp, term->wcTo, ldata->size);
 
 	    lchars = term->ltemp;
 	} else {
-		lchars = term->post_bidi_cache[i].chars;
+	    lchars = term->post_bidi_cache[scr_y].chars;
 	}
+    } else {
+	lchars = NULL;
+    }
+
+    return lchars;
+}
+
+/*
+ * Given a context, update the window. Out of paranoia, we don't
+ * allow WM_PAINT responses to do scrolling optimisations.
+ */
+static void do_paint(Terminal *term, Context ctx, int may_optimise)
+{
+    int i, j, our_curs_y, our_curs_x;
+    int rv, cursor;
+    pos scrpos;
+    wchar_t *ch;
+    int chlen;
+    termchar cursor_background;
+#ifdef OPTIMISE_SCROLL
+    struct scrollregion *sr;
+#endif /* OPTIMISE_SCROLL */
+
+    cursor_background = term->basic_erase_char;
+
+    chlen = 1024;
+    ch = snewn(chlen, wchar_t);
+
+    rv = (!term->rvideo ^ !term->in_vbell ? ATTR_REVERSE : 0);
+
+    /* Depends on:
+     * screen array, disptop, scrtop,
+     * selection, rv, 
+     * cfg.blinkpc, blink_is_real, tblinker, 
+     * curs.y, curs.x, cblinker, cfg.blink_cur, cursor_on, has_focus, wrapnext
+     */
+
+    /* Has the cursor position or type changed ? */
+    if (term->cursor_on) {
+	if (term->has_focus) {
+	    if (term->cblinker || !term->cfg.blink_cur)
+		cursor = TATTR_ACTCURS;
+	    else
+		cursor = 0;
+	} else
+	    cursor = TATTR_PASCURS;
+	if (term->wrapnext)
+	    cursor |= TATTR_RIGHTCURS;
+    } else
+	cursor = 0;
+    our_curs_y = term->curs.y - term->disptop;
+    {
+	/*
+	 * Adjust the cursor position:
+	 *  - for bidi
+	 *  - in the case where it's resting on the right-hand half
+	 *    of a CJK wide character. xterm's behaviour here,
+	 *    which seems adequate to me, is to display the cursor
+	 *    covering the _whole_ character, exactly as if it were
+	 *    one space to the left.
+	 */
+	termline *ldata = lineptr(term->curs.y);
+	termchar *lchars;
+
+	our_curs_x = term->curs.x;
+
+	if ( (lchars = term_bidi_line(term, ldata, our_curs_y)) != NULL) {
+	    our_curs_x = term->post_bidi_cache[our_curs_y].forward[our_curs_x];
 	} else
 	    lchars = ldata->chars;
 
+	if (our_curs_x > 0 &&
+	    lchars[our_curs_x].chr == UCSWIDE)
+	    our_curs_x--;
+
+	unlineptr(ldata);
+    }
+
+    /*
+     * If the cursor is not where it was last time we painted, and
+     * its previous position is visible on screen, invalidate its
+     * previous position.
+     */
+    if (term->dispcursy >= 0 &&
+	(term->curstype != cursor ||
+	 term->dispcursy != our_curs_y ||
+	 term->dispcursx != our_curs_x)) {
+	termchar *dispcurs = term->disptext[term->dispcursy]->chars +
+	    term->dispcursx;
+
+	if (term->dispcursx > 0 && dispcurs->chr == UCSWIDE)
+	    dispcurs[-1].attr |= ATTR_INVALID;
+	if (term->dispcursx < term->cols-1 && dispcurs[1].chr == UCSWIDE)
+	    dispcurs[1].attr |= ATTR_INVALID;
+	dispcurs->attr |= ATTR_INVALID;
+
+	term->curstype = 0;
+    }
+    term->dispcursx = term->dispcursy = -1;
+
+#ifdef OPTIMISE_SCROLL
+    /* Do scrolls */
+    sr = term->scrollhead;
+    while (sr) {
+	struct scrollregion *next = sr->next;
+	do_scroll(ctx, sr->topline, sr->botline, sr->lines);
+	sfree(sr);
+	sr = next;
+    }
+    term->scrollhead = term->scrolltail = NULL;
+#endif /* OPTIMISE_SCROLL */
+
+    /* The normal screen data */
+    for (i = 0; i < term->rows; i++) {
+	termline *ldata;
+	termchar *lchars;
+	int dirty_line, dirty_run, selected;
+	unsigned long attr = 0, cset = 0;
+	int updated_line = 0;
+	int start = 0;
+	int ccount = 0;
+	int last_run_dirty = 0;
+	int *backward;
+
+	scrpos.y = i + term->disptop;
+	ldata = lineptr(scrpos.y);
+
+	dirty_run = dirty_line = (ldata->lattr !=
+				  term->disptext[i]->lattr);
+	term->disptext[i]->lattr = ldata->lattr;
+
+	/* Do Arabic shaping and bidi. */
+	lchars = term_bidi_line(term, ldata, i);
+	if (lchars) {
+	    backward = term->post_bidi_cache[i].backward;
+	} else {
+	    lchars = ldata->chars;
+	    backward = NULL;
+	}
+
 	for (j = 0; j < term->cols; j++) {
 	    unsigned long tattr, tchar;
 	    termchar *d = lchars + j;
 	    int break_run, do_copy;
-	    scrpos.x = j;
+	    scrpos.x = backward ? backward[j] : j;
 
 	    tchar = d->chr;
 	    tattr = d->attr;
@@ -5341,10 +5396,20 @@ void term_mouse(Terminal *term, Mouse_Button braw, Mouse_Button bcooked,
 	x = term->cols - 1;
 
     selpoint.y = y + term->disptop;
-    selpoint.x = x;
     ldata = lineptr(selpoint.y);
+
     if ((ldata->lattr & LATTR_MODE) != LATTR_NORM)
-	selpoint.x /= 2;
+	x /= 2;
+
+    /*
+     * Transform x through the bidi algorithm to find the _logical_
+     * click point from the physical one.
+     */
+    if (term_bidi_line(term, ldata, y) != NULL) {
+	x = term->post_bidi_cache[y].backward[x];
+    }
+
+    selpoint.x = x;
     unlineptr(ldata);
 
     if (raw_mouse) {

terminal.h

@@ -68,6 +68,7 @@ struct termline {
 struct bidi_cache_entry {
     int width;
     struct termchar *chars;
+    int *forward, *backward;	       /* the permutations of line positions */
 };
 
 struct terminal_tag {